Putamen
| Latin = | GraySubject = 189 | GrayPage = 34 | Image = Gray744.png | Caption = Coronal section of brain through anterior commissure. (Putamen labeled at center right.) | Image2 = Gray718.png | Caption2 = Coronal section of brain through intermediate mass of third ventricle. (Putamen labeled at top.) | IsPartOf = | Components = | Artery = | Vein = | BrainInfoType = hier | BrainInfoNumber = 212 | MeshName = Putamen | MeshNumber = | DorlandsPre = p_43 | DorlandsSuf = 12681480 | }} The putamen is a round structure located at the base of the forebrain (telencephalon). The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures in the basal ganglia. Through various pathways, it is mainly connected to the substantia nigra and globus pallidus. The main function of the putamen is to regulate movements and influence various types of learning. It uses dopamine mechanisms to perform its functions. The putamen also plays a role in degenerative neurological disorders, like Parkinson’s disease. History The word "putamen" is from Latin, referring to that which falls off in pruning, from "puto", to prune. It is pronounced pyu-ta´men. Very few studies were conducted in the past that were focused specifically on the putamen. However, there have been many studies done on the basal ganglia and how the brain structures that comprise it interact with each other. In the 1970’s, the first single unit recordings were done with monkeys monitoring pallidal neurons activity related to movement. Anatomy The putamen is a structure in the forebrain, and with the caudate nucleus it forms the dorsal striatum. The caudate and putamen contain the same types of neurons and circuits—many neuroanatomists consider the dorsal striatum to be a single structure, divided into two parts by a large fiber tract, the internal capsule, passing through the middle. Together with the globus pallidus, it makes up the lenticular nucleus. The putamen is also the outer most portion of the basal ganglia. These are a group of nuclei in the brain that are interconnected with the cerebral cortex, thalamus, and brain stem. The other parts of the basal ganglia include the dorsal striatum, substantia nigra, nucleus accumbens, and the subthalamic nucleus. The basal ganglia in mammals are associated with motor control, cognition, emotions, and learning. Basal ganglia are located on the left and right sides of the brain, and have rostral and caudal divisions. The putmen is located in the rostral division as part of the striatum. The basal ganglia receive input from the cortex via the striatum. The putamen is interconnected with the following structures: Caudate Nucleus The caudate works with the putamen to receive the input from cerebral cortex. They can be considered the “entrance” to the basal ganglia. The nucleus accumbens and medial caudate receive input from frontal cortex and limbic regions. The putamen and caudate are jointly connected with the substantia nigra, but most of their output goes to the globus pallidus. Substantia Nigra The substantia nigra contains two parts: the substantia nigra pars compacta (SNpc) and the substantia nigra pars reticulata (SNpr). The SNpc obtains input from the putamen and caudate, and sends information back. The SNpr also obtains input from the putamen and caudate. However, it sends the input outside the basal ganglia to control head and eye movements. The SNpc produces dopamine, which is crucial for movements. The SNpc is the part which degenerates during Parkinson's disease1. Globus Pallidus The globus pallidus contains two parts: the globus pallidus externa (GPe) and the globus pallidus interna (GPi). Both regions acquire input from the putamen and caudate and communicate with the subthalamic nucleus. However, mostly the GPi sends the inhibitory output from the basal ganglia to the thalamus. The GPi also sends a few projections to parts of the midbrain, which have been assumed to affect posture control1. Physiology Types of Pathways In order to control movements, the putamen must interact with the other structures that make up the basal ganglia along with it. These include the caudate nucleus and globus pallidus. These two structures and the putamen interact through a series of direct and indirect inhibitory pathways. The direct pathway consists of two inhibitory pathways that go from the putamen to the substantia nigra and the internal globus pallidus. This pathway uses the neurotransmitters dopamine, GABA and substance P. The indirect pathway consists of three inhibitory pathways that go from the putamen and caudate nucleus to the external region of the globus pallidus. This pathway uses dopamine, GABA and enkephalin. When there is interplay and tangling between the two types of pathways, involuntary movements occur. Dopamine One of the main neurotransmitters that is regulated by the putamen is dopamine. When a cell body fires an action potential, dopamine is released from the presynaptic terminals of the putamen and the caudate nucleus. Since projections from the putamen and caudate nucleus modulate the dendrites of the substantia nigra, the dopamine influences the substantia nigra, which affects motor planning. This same mechanism is involved in addiction. In order to control the amount of dopamine in the synaptic gap and the amount of dopamine binding to post synaptic terminals, dopaminergic terminals take up the excess dopamine. Other Neurotransmitters The putamen also plays a role in regulating other neurotransmitters. It releases GABA, enkephalin, substance P, acetylcholine, and it receives serotonin and glutamate. The majority of these neurotransmitters play a role in motor control2. Function: Motor Skills While the putamen has many functions, it has been concluded that it has no specific specialization. However, since the putamen is interconnected with so many other structures, it works in conjunction with them to control many types of motor skills. These include controlling motor learning, motor performance and tasks3, motor preparation4, specifying amplitudes of movement5, and movement sequences6. Some neurologists hypothesize that the putamen also plays a role in the selection of movement (like in Tourette Syndrome) and the automatic performance of previously learned movements (like in Parkinson’s disease).7 In one study it was found that the putamen controls limb movement. The goal of this study was to determine whether particular cell activity in the putamen of primates were related to the direction of limb movement or to the underlying pattern of muscular activity. Two monkeys were trained to performed tasks that involved the movement of loads. The tasks were created so movement could be distinguished from muscle activity. Neurons in the putamen were selected for monitoring only if they were related both to the task and to arm movements outside the task. It was shown that 50% of the neurons that were monitored were related to the direction of movement independent of the load8. Another was done to investigate movement extent and speed using PET mapping of regional cerebral blood flow in 13 humans. Movement tasks were performed with a joystick-controlled cursor. Statistical tests were done to calculate the extent of movements and what regions of the brain they correlate to. It was found that “increasing movement extent was associated with parallel increases of rCBF in bilateral basal ganglia (BG; putamen and globus pallidus) and ipsilateral cerebellum”. This not only shows that the putamen affects movement but also shows that it integrates with other structures in order to perform tasks9. One study was done in order to specifically investigate how the basal ganglia influences the learning of sequential movements. Two monkeys were trained to press a series of buttons in a sequence. The methods used were designed to be able to monitor well-learned tasks and new tasks. Muscimol was injected into various parts of the basal ganglia, and it was found that “the learning of new sequences became deficient after injections in the anterior caudate and putamen, but not the middle-posterior putamen”. This shows that different areas of the striatum are utilized when performing various aspects of the learning of sequential movements10. Role in Learning In many studies, it has become apparent that the putamen plays a role in many types of learning. Some examples are listed below: Reinforcement and Implicit Learning Along with various types of movement, the putamen also affects reinforcement learning and implicit learning11. Reinforcement learning is interacting with the environment and catering actions to maximize the outcome. Implicit learning is a passive process where people are exposed to information and acquire knowledge through exposure. Although the exact mechanisms are not known, it is clear that dopamine and tonically active neurons play a key role here. Tonically active neurons are cholinergic interneurons that fire during the entire duration of the stimulus and fire at about 0.5-3 impulses per second. Tonic neurons are the opposite and only fire an action potential when movement occurs12. Category Learning One particular study used patients with focal lesions on the basal ganglia (specifically the putamen) due to stroke in order to study category learning. The advantage to using these types of patients is that dopaminergic projections to the prefrontal cortex are more likely to be in tact. Also, in these patients, it is easier relate specific brain structures to function because the lesion only occurs in a specific place. The goal of this study was to determine whether or not these lesions affect rule-based and information-integration task learning. Rule-based tasks are learned via hypothesis-testing which is dependant on working memory. Information-integration tasks are ones where the accuracy is maximized when information from two sources are integrated at a pre-decisional stage, which follows a procedural-based system. Seven participants with basal ganglia lesions were used in the experiment, along with nine control participants. It is important to note that the caudate was not affected. The participants were tested for each type of learning during separate sessions, so the information processes would not interfere with each other. During each session, participants sat in front of a computer screen and various lines were displayed. These lines were created by using a randomization technique where random samples were taken from one of four categories. For ruled-based testing, these samples were used to construct lines of various length and orientation that fell into these four separate categories. After the stimulus was displayed, the subjects were asked to press 1 of 4 buttons to indicate which category the line fell into. The same process was repeated for information-integration tasks, and the same stimuli were used, except that the category boundaries were rotated 45°. This rotation causes the subject to integrate the quantitative information about the line before determining what category it is in. It was found that subjects in the experimental group were impaired while performing rule-based tasks, but not information-integration ones. After statistical testing, it was also hypothesized that the brain began using information-integration techniques to solve the rule-based learning tasks. Since rule-based tasks use the hypothesis-testing system of the brain, it can be concluded that the hypothesis-testing system of the brain was damaged/weakened. It is known that the caudate and working memories are part of this system. Therefore, it was confirmed that the putamen is involved category learning, competition between the systems, feed-back processing in rule-based tasks, and is involved in the processing of pre-frontal regions (which relate to working memory and executive functioning). Now it is known that not only the basal ganglia and caudate affect category learning13. New Research See: Hatred Recent, tentative studies have suggested that the putamen may play a role in the “hate circuit” of the brain. A recent study was done in London by the department of cell and developmental biology at University College London. An fMRI was done on patients while they viewed a picture of people they hated and people who were “neutral”. During the experiment, a hate score was recorded for all pictures. The activity in sub-cortical areas of the brain imply that the hate circuit involves the putamen and insula. It has been hypothesized that the “putamen plays a role in the perception of contempt and disgust, and may be part of the motor system that's mobilized to take action”.These scientists have also found that the amount of activity in the hate circuit correlates with the amount of hate a person declares, which could have legal implications concerning malicious crimes14. Pathology Parkinson’s Disease After discovering the function of the putamen, it has become apparent to neurologists that the putamen and basal ganglia play an important role in Parkinson’s Disease and other diseases that involve the degeneration of neurons15. Parkinson’s diseases is the slow and steady loss of dopaminergic neurons in substantia nigra pars compacta. In Parkinson’s Disease the putamen plays a key role because its inputs and outputs are interconnected to the substantia nigra and the globus pallidus. In Parkinson’s Diseases the activity in direct pathways to interior globus pallidus decreases and activity in indirect pathways to external globus pallidus increases. Together these actions cause excessive inhibition of the thalamus. This is why Parkinson’s patients have tremors and have trouble performing involuntary movements. It has also been noted that Parkinson’s patients have a difficult time with motor planning. They must think about everything they do and cannot perform instinctive tasks without focusing on what they are doing. Other Diseases and Disorders The following diseases and disorders are linked with the putamen: *Cognitive decline in Alzheimer’s disease16 *Huntington's disease *Wilson's disease *Dementia with Lewy bodies *Corticobasal degeneration *Tourette syndrome *Schizophrenia *Depression The Putamen in Other Animals The putamen in humans is similar in structure and function to other animals. Therefore, many studies regarding the putamen have been done on animals (monkeys, rats, etc.), as well as humans. Additional images Image:Telencephalon-Horiconatal.jpg|Horizontal section of right cerebral hemisphere. Image:Constudoverbrain.gif|Brain Image:Human brain frontal (coronal) section description 2.JPG|Human brain frontal (coronal) section Image:Putamen.jpg|Horizontal slice of MRI-image showing the putamen. The other nuclei of the basal ganglia (caudate nucleus and globus pallidus) can be seen as well. References 1Alexander GE, Crutcher MD. Functional architecture of basal ganglia circuits: neural substrates of parallel processing. Trends Neurosci. 1990 Jul;13(7):266-71. Review. 2Crutcher, Michael D.Telephone Interview. 19 November 2008. 3DeLong MR, Alexander GE, Georgopoulos AP, Crutcher MD, Mitchell SJ, Richardson RT. Role of basal ganglia in limb movements. Hum Neurobiol. 1984;2(4):235-44. 4Alexander GE, Crutcher MD. Preparation for movement: neural representations of intended direction in three motor areas of the monkey. J Neurophysiol. 1990 Jul;64(1):133-50. 5Delong MR, Georgopoulos AP, Crutcher MD, Mitchell SJ, Richardson RT, Alexander GE. Functional organization of the basal ganglia: contributions of single-cell recording studies. Ciba Found Symp. 1984;107:64-82. 6Marchand, William R. a c d; Lee, James N. a c d; Thatcher, John W. b c; Hsu, Edward W. a c d; Rashkin, Esther c; Suchy, Yana c d; Chelune, Gordon c d; Starr, Jennifer a c; Barbera, Sharon Steadman c. Putamen coactivation during motor task execution. Neuroreport. 19(9):957-960, June 11, 2008. 7Griffiths P. D.; Perry R. H.; Crossman A. R. A detailed anatomical analysis of neurotransmitter receptors in the putamen and caudate in Parkinson's disease and Alzheimer's disease. Neuroscience Letters 0304-3940 GRIFFITHS yr:1994 vol:169 iss:1-2 pg:68 8Crutcher MD, DeLong MR. Single cell studies of the primate putamen. II. Relations to direction of movement and pattern of muscular activity. Exp Brain Res. 1984;53(2):244-58. 9Turner RS, Desmurget M, Grethe J, Crutcher MD, Grafton ST. Motor subcircuits mediating the control of movement extent and speed. J Neurophysiol. 2003 Dec;90(6):3958-66. Epub 2003 Sep 3. 10Shigehiro Miyachi, Okihide Hikosaka, Kae Miyashita, Zoltán Kárádi, Miya Kato Rand. Differential roles of monkey striatum in learning of sequential hand movement. Exp Brain Res (1997) 115:1–5. 11Mark G. Packard and ¬ Barbara J. Knowlton. Learning and Memory Functions of the Basal Ganglia. Annual Review of Neuroscience. Vol. 25: 563-593, March 2002. 12Hiroshi Yamada, Naoyuki Matsumoto, and Minoru Kimura. Tonically Active Neurons in the Primate Caudate Nucleus and Putamen Differentially Encode Instructed Motivational Outcomes of Action. The Journal of Neuroscience, April 7, 2004, 24(14):3500-3510 13Ell SW, Marchant NL, Ivry RB. 2006. Focal putamen lesions impair learning in rule-based, but not information-integration categorization tasks. Neuropsychologia 44:1737-51 14Zeki S, Romaya JP. Neural Correlates of Hate. PLoS ONE 3(10): e3556. October 29, 2008. 15DeLong MR, Wichmann T. Circuits and circuit disorders of the basal ganglia. Arch Neurol. 2007 Jan;64(1):20-4. Review. 16de Jong LW, van der Hiele K, Veer IM, Houwing JJ, Westendorp RG, Bollen EL, de Bruin PW, Middelkoop HA, van Buchem MA, van der Grond J. Strongly reduced volumes of putamen and thalamus in Alzheimer's disease: an MRI study. Brain (20 November 2008), awn278. External links * * * * Diagram at uni-tuebingen.de Category:Basal ganglia Category:Cerebrum